111 research outputs found
Soil organic matter characteristics, biochemical activity and antioxidant capacity in Mediterranean land use systems
No full textThe characteristics of soil quality were measured in adjacent agricultural (horticultural cropping sequence, HC), native grassland (naturally grazed, NG) and forest (indigenous wood of holm-oak, F) soils. The objective of the research was to assess the influence of different land uses on soil organic matter characteristics, biochemical activity and antioxidant capacity in selected fields of the Mediterranean environment in central Italy under a specific climatic regime.Land use induced significant changes in the content and quality of soil organic matter, biochemical activity and antioxidant capacity, with more pronounced differences between soils under HC and F than soils under HC and NG. The HC soil showed the lowest amounts of total organic carbon (TOC), microbial biomass C (MB-C), water-soluble organic C (WSOC), water- and alkali-soluble phenols. The organic matter of HC was characterized by the lowest percentage of MB-C and of light fraction carbon (LF-C). The dehydrogenase activity (DH-ase), metabolic potential (MP), hydrolyzing coefficient (HyC), potentially mineralizable C (C 0) and C mineralized (C m) were clearly lower in HC. The specific respiration activity of biomass (qCO 2) was the highest in HC soil (1.3μg CO 2-CμgbiomassC -1) and lowest in F soil (0.5μgCO 2-CμgbiomassC -1) and was inversely related with pH, TOC and MB-C contents. The antioxidant capacity of soils (TEAC) was the highest in NG and related to the amount of alkali-soluble phenols. The rate constant of organic matter mineralization (k) appeared to depend on TEAC rather than the relative amounts of the labile C pools. These results seem to explain the role of phenols as controller of the mineralization rate of organic matter
Characterization and origin of organic and inorganic pollution in urban soils in Pisa (Tuscany, Italy).
No full textWe assessed the quality of 31 urban soils in Pisa by analyzing total petroleum hydrocarbons (TPH), Cd, Cr, Cu, Hg, Mn, Ni, Pb, Zn and the platinum group (PGEs). The risk was evaluated by the geological accumulation index (Igeo) and the enrichment factor (EF). Results were compared with those obtained from a non-urban site and with the quantitative limits fixed by Italian legislation. In nearly all the monitored sites, the legal limit for TPH of 60 mg/kg in residential areas was exceeded, indicating widespread and intense pollution throughout the entire city area. The Igeo indicated no Cd, Cu, Mn, Ni and Zn pollution and minimal Pb and Cr pollution, due to anthropogenic enrichment. Legal Hg and Zn limits of 1 and 150 mg/kg respectively were exceeded in about 20% of sites, Cd (2 mg/kg), Cr (150 mg/kg) and Cu (120 mg/kg) in only one site, the Ni legal limit of 120 mg/kg was never exceeded. Some urban soils showed a higher Hg level than the more restrictive legal limit of 5 mg/kg concerning areas for industrial use. Based on the soluble, exchangeable and carbonate-bound fractions, Mn and Zn showed the highest mobility, suggesting a more potential risk of soil contamination than the other metals. The TPH and both Cr and Hg amounts were not correlated with any of the other monitored metals. The total contents of Cd, Pb, Zn and Cu in soils were positively correlated with each other, suggesting a common origin from vehicular traffic. The PGE values (Pt and Pd) were below the detection limits in 75% - 90% of the monitored areas, suggesting that their accumulation is at an early stage
Applicazione di bio-stimolanti al suolo contaminato da idrocarburi: effetti sulla biodegradazione.
No full textLa persistenza degli idrocarburi policiclici aromatici (IPA) nell'ambiente dipende dalle caratteristiche fisiche e chimiche del composto stesso e da una serie di fattori fisici, chimici, biologici e ambientali che possono influenzarne la velocità e il grado di degradazione. Gli IPA sono degradati da foto-ossidazione e ossidazione chimica, ma la degradazione biologica è probabilmente la via prevalente anche in funzione delle molte specie di batteri, funghi e alghe che possono degradarli. La degradazione microbica di idrocarburi contenenti fino a tre anelli (naftalene, fenantrene) è stata ampiamente studiata, ma vi è scarsità di informazioni sulla degradazione degli idrocarburi contenenti un numero maggiore di strutture aromatiche, come il pirene o il benzo[a]pirene, che non vengono completamente degradati a causa della loro bassa solubilità in acqua, alta energia di risonanza ed elevata tossicità.
In questo lavoro viene valutata in incubazioni di laboratorio l'efficacia di 2 prodotti biostimolanti commercializzati dalla Valagro sulla degradazione degli idrocarburi fenantrene e pirene nel suolo. A tal fine un suolo agrario è stato contaminato con fenantrene e pirene (500 μg∙g-1) e successivamente trattato con due diverse dosi di Viva® e AU15%®. Le dosi (8 e 16 g∙kg-1 di suolo) corrispondono ad una applicazione rispettivamente di 25 e 50t di sostanza organica ha-1. I campioni sono stati analizzati nel tempo (45 gg) per monitorare il loro contenuto di idrocarburi, ATP, lipasi e deidrogenasi.
I principali risultati indicano che il contenuto di ATP (biomassa microbica) subisce un forte incremento nelle tesi in cui sono stati distribuiti i bio-stimolanti, particolarmente evidente in seguito all'applicazione di Viva® distribuito alla dose più elevata. Sebbene fenantrene e pirene costituiscano un possibile substrato per la lipasi, l’applicazione dei 2 composti non ha influenzato l'attività dell’enzima. L’attività lipasica appare invece notevolmente stimolata dall’aggiunta dei 2 biostimolanti, in particolare da AU15%®. Soltanto Viva® applicato alla dose più elevata riesce a stimolare l'attività deidrogenasica con valori che, dopo una settimana di incubazione, risultavano 3 volte maggiori di quelli delle altre tesi. La dinamica e l'intensità delle perdite dei 2 idrocarburi è stata chiaramente influenzata dal tipo di composto: il fenantrene veniva rapidamente e quasi completamente degradato, mentre per il pirene si registrava una minor diminuzione della sua concentrazione. Non sembra emergere un rapporto diretto tra la dinamica di degradazione degli idrocarburi e i parametri biologici testati. La presenza dei 2 idrocarburi non ha determinato particolari effetti sul contenuto di ATP e sulle attività enzimatiche analizzate. L'applicazione dei biostimolanti ha provocato generalmente notevoli modificazioni del contenuto di ATP e dei livelli delle attività enzimatiche, mentre non sembra aver influito su velocità ed entità della decomposizione dei 2 contaminanti
Short-term releases of CO2 from newly mixed biochar and calcareous soil.
No full textThe work aims to quantify native organic C mobilized in one calcareous soil in the 21 days after addition of biochar at a range of high to very high doses. The experiment was carried out in unplanted microcosms and CO2 flux was used as a measure of net mineralization. A rapid methodological approach, which does not require 13C as a tracer, was used to assess any priming effects induced by the biochar. The amount of CO2-C mobilized was small relative to the amount of biochar C and proportional to the amount of the biochar added. The additional CO2–C was similar to the content of the WSOC of the biochar added in each respective dose. No interaction with native soil C, i.e. priming effect, was observed
Biological activity and functional diversity of agricultural soil amended with sewage sludge.
No full textThe biological effects of applying sewage sludge (SS) to agricultural soil (at a low rate of 22.5, LRS, and a high rate of 45 t ha-1 dry basis, HRS) were monitored over a 120-d experimental period.
The biological activity was monitored by dehydrogenase, catalase, urease, protease, alkaline phosphatase, arylsulphatase and β-glucosydase activities. Selected characteristics also included soil microbial biomass carbon (MBC) and community level physiological profiling (CLPP), indicating the microbial functional diversity of soil (catabolic potential) and assessed using Richness (R) and Shannon–Weaver (H) indexes. All the enzyme activities were strongly affected by both rates of SS applications. After a rapid increase in the early phases of the experiment, enzyme activities decreased sharply and remained almost stable during the last stages of the trial period. Microbial biomass carbon was also influenced by SS addition, however during the incubation period of 120 days, it remained at high levels only at HRS. The H index increased significantly with the increasing SS applications. Differences in the functional diversity of soil microbial communities were found. For both doses, there was an increase in biodiversity over time, reaching about 9% compared to the control
Antioxidant capacity in urban soils
No full textThe quality of soils in 31 urban green areas in Pisa was assessed in terms their soil antioxidant systems
by measuring antioxidant capacity (TEAC) and phenol substances, soil basal respiration, community
level physiological profile (CLPP), expressed as average well color development (AWCD), community
metabolic diversity (CMD), the Shannon–Weaver index (H), and soil enzyme activities. The urban results
were compared to an extra-urban control area (near the S. Rossore-Migliarino-Massaciuccoli Natural
Park).
The soils of the greenspaces of Pisa city were mostly sandy, subalkaline, lightly calcareous, with a rather
high (mean of 3.27
±
1.24 gC 100 g−1 dry soil) and variable (1.32–7.57 gC 100 g−1 dry soil) organic matter
content.
There were little differences in the functional diversity (AWCD) of soil microbial communities. Dehydrogenase,
catalase, alkaline phosphatase, B-glucosidase and lipase showed little variability among soils
while arylsulphatase, protease and urease activities varied within a fairly wide range of values. Values of
the alkali-and water-soluble TEAC of urban soils varied within quite large ranges (2.53–11.45 mM g−1 soil
and 0.11–2.91 mM g−1 dry soil, respectively) and were generally higher than those of control. TEAC and
phenol substances, both in alkaline and water extracts, were closely correlated (r > 0.850, P
≤
0.01) and
were also positively correlated with soil organic C, AWCD, CMD and, H. With the exception of dehydrogenase,
the soil antioxidant system showed positive correlations with the enzymatic activities and soil
basal respiration. The antioxidant system and soil basal respiration can be considered useful indicators
of the soil biological status and soil quality in the examined urban soils
Effect of Biochar, Green Compost, and Vermicompost on the Quality of a Calcareous Soil: A 1-Year Laboratory Experiment
No full textChanges in the chemical and biological characteristics of a calcareous soil by the addition of green compost (GC), vermicompost (VC), biochar, biochar + GC, and biochar + VC were evaluated during a 360-day laboratory incubation. The GC and the VC treatments lowered the soil pH and increased the total and dissolved organic C, microbial biomass C, microbial quotient, alkaline phosphatase (AP-ase) and specific AP-ase, dehydrogenase (DH-ase) and specific DH-ase, and metabolic potential. The improvement in the biological activity of the soil was more notable and permanent with VC than GC. The biochar treatment temporarily increased the pH of the calcareous soil (pH 8.2) up to a maximum of 8.57, showed the greatest increase of total organic C, did not change dissolved organic C and microbial biomass C, and induced small effects on soil biological activities. When mixed with biochar (biochar + GC and biochar + VC), composts led to higher organic C mineralization; dissolved organic C, biomass C, and DH-ase activity; and did not change the metabolic quotient, specific AP-ase, and specific DH-ase activities. The AP-ase activity of biochar was enhanced only by the addition of VC, although in a nonadditive way. Metabolic potential was more than halved by the GC and was not changed by the VC. Overall, our study shows that the incorporation of both composts, particularly VC, into calcareous soils may improve soil quality, whereas biochar could have benefits for C sequestration. In addition, the mixing of GC, and especially VC with biochar, increased some soil quality parameters compared with the biochar-only treatment
Are the physiological and biochemical characteristics in dandelion plants growing in an urban area (Pisa, Italy) indicative of soil pollution?
No full textPhysiological and biochemical characteristics
were evaluated in dandelion plants (Taraxacum
officinale) growing naturally in an urban environment.
The study area was located in Pisa, Italy, and 27 sites in
the municipality were chosen to assess the biochemical
and physiological features of dandelion plants and the
trace metal content in the urban soil. Concentrations of
elements including, Cr, Cu, Mn and Zn were analysed in
the soil together with dandelion shoot and root tissues
collected from the various sites. Chlorophyll a fluorescence
analysis, the pigment content, antioxidant power
and phenol content were determined in dandelion. The
results showed very limited soil pollution due to trace
metals in the urban sites. However, dandelion showed
Zn uptake and translocation although no damage was
observed in the plants. Our results highlight that
dandelion plants are able to survive in a constrained
environment thanks to the high phenol content which
is effective in combatting the oxidative stress induced
by heavy metals
Effetti del biochar sulla mineralizzazione della sostanza organica del suolo: prove di laboratorio.
No full textUna potenziale via di abbattimento dei livelli crescenti di CO2 nell'atmosfera è l'uso della pirolisi per convertire la biomassa vegetale in una forma più stabile di carbonio (biochar), che può poi essere applicato al suolo.
Allo scopo di valutare l'interazione tra biochar e sostanza organica del suolo e di mettere in evidenza eventuali priming effects indotti dal materiale, è stata effettuata un’incubazione di breve periodo, in laboratorio, trattando un suolo con dosi di applicazione di 0, 2, 4, 6, 8 e 10% in peso, misurando per 21 giorni la respirazione microbica mediante lo sviluppo di CO2.
Gli effetti del biochar sulla mineralizzazione della sostanza organica nativa (priming effect) sono stati valutati attraverso la comparazione tra il rilascio di CO2 dal suolo (controllo) e quello misurato nelle miscele di biochar e suolo. A tal fine è stata calcolata una retta di regressione con i dati cumulativi di C-CO2 emesso dalle miscele biochar–suolo rispetto al C fornito con il materiale, che ha permesso di stimare il C-CO2 emesso ad una dose di applicazione pari a zero. Il valore ottenuto è stato infine confrontato con il corrispondente dato misurato nel controllo, ottenendo così il priming ratio.
I risultati mostrano che dal suolo ammendato con biochar è stata rilasciata una maggior quantità di carbonio sottoforma di CO2 rispetto al controllo, con aumenti lineari rispetto alla quantità di C aggiunto.
L’assenza di priming effect, confermato dal valore prossimo a 1 del priming ratio, indica che l’incremento di CO2 non proviene da un maggior rilascio di carbonio della sostanza organica nativa e quindi che una frazione del carbonio del biochar viene perduta per respirazione microbica. La perdita di C da parte del biochar, pari a circa 0.006%, è tuttavia molto modesta e, vista la netta tendenza alla diminuzione nell’entità della mineralizzazione già durante la breve durata dell’incubazione, è presumibile che le perdite di C del materiale nel lungo periodo siano nettamente inferiori alla quantità dell’elemento aggiunto al suolo con l’ammendamento. Considerato il lunghissimo tempo medio di residenza nel suolo del carbonio del biochar, il modesto rilascio di carbonio per respirazione microbica non pare quindi compromettere la capacità del materiale di contribuire al sequestro di C nell’ecosistema suolo
Changes in biological properties and antioxidant capacity of an agricultural soil amended with sewage sludge
No full textThe effects of applying sewage sludge (SS) to agricultural soil (at low rate
of 22.5, LRS, and at high rate of 45 t ha−1 dry basis, HRS) were monitored
over a 120-d experimental period. Total organic carbon (TOC), water-
soluble organic carbon (WSOC), alkali-soluble phenols, basal respiration, 10
specific enzyme activity, dehydrogenase activity (DH-ase), metabolic
potential (MP) and FDA-hydrolytic activity (FDA) were strongly increased
by both rates of SS applications. In the SS amended soil, about 70% of
the organic C added with the material remained at the end of the
experiment. Basal respiration increased with increasing SS doses. The 15
specific enzyme activity and the MP indicate an increase in the enzyme
activity in soil.
AQ10
The addition of SS led to higher values than the control of all the
tested parameters up to the end of the experimental period. The anti-
oxidant capacity (trolox equivalent antioxidant capacity, TEAC) was influ- 20
enced by SS addition only when applied at HRS. After 120 days only HRS
value of TEAC (5.13 mM g−1) was higher than control (4.09 mM g−1). The
pattern of TEAC did not enable any link to be established between
antioxidant capacity and both alkali-soluble phenols and basal respira-
tion in soil
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